1. Technical Field
The present application relates to a food and beverage industry membrane valve structure for use in food or beverage processing or handling. The membrane valve structure is utilized to control the movement of food or beverages through a chamber in a food or beverage processing or handling machine.
The present application further relates to a membrane valve with a membrane which is mounted in a sealed manner in a valve housing and separates the control chamber and/or the movable valve rod from the product chamber, with a support device for the stabilization of the membrane used as described herein below.
2. Background Information
In general, membrane valves are valves that utilize a thin flexible membrane to separate chambers in a device to contain a product, such as, in the present application, a food or beverage, in one chamber, while simultaneously minimizing the entry of food or beverage product into the other chamber or chambers. The membrane valve also protects the food or beverage product from contamination by contaminants from the other chamber or chambers, such as dust or dirt. This function is important to protect the food or beverage product. The membrane valve must be sufficiently thin to be sufficiently flexible to permit movement of a corresponding valve stem, but also must be sufficiently thick to be strong enough to withstand wear and tear during operation of the membrane valve. Such wear and tear can be caused by the movement of the valve during operation, as well as by pressure that can build up in the chamber, which pressure can cause deformations in the membrane.
Membrane valves of this type include, for example, pneumatically controlled pressure governor valves or pressure vessel valves to maintain constant process pressures in industrial process equipment, in the food and/or beverage industry, for example, as well as in the pharmaceutical and chemical industry. The functional principle of maintaining a constant pressure is based on reducing or enlarging the open flow cross section at the valve seat by means of the adjustable valve stem which is connected with the regulation membrane. Membrane valves of this type are used for the general actuation of product flows. Thin disc membranes made of PTFE are used as a seal between the valve housing that is incorporated into the pipeline and the movable stem rod. Disc membranes of this type have are fixed on the outside and on the inside, or they are fixed only on the outside and on the inside are connected in one piece with the stem. The disc membranes must on one hand be thin and flexible so that they can easily track the movement of the stem rod, and on the other hand they must be capable of withstanding the pressure forces exerted by the product. The product pressure results in a gradual deformation of the membrane in the pressure-bearing area and finally leads to the rupture of the membrane. Tensile forces also act on the inner and outer membrane fastenings, which have a negative impact on the quality of the seal and on the useful life of the membrane. In real installations, especially during startup, pressure peaks frequently occur as a result of defects in the operation and control of the process. The membrane material also has a lower strength at elevated temperatures, e.g. at the temperatures used for steam sterilization. To relieve the pressure on the disc membrane, membrane supports on the side facing away from the pressure are known, such as those that are made rubber with vulcanized fabric plies, or movable metal segments that are supported internally or externally.
On control valves of the prior art, the configuration of the membrane wall represents a problem. For a variety of reasons, this membrane wall must often have a significantly larger diameter than the part of the movable valve body that is fastened to the membrane wall. This makes it difficult to achieve a high control accuracy. More precisely, the problem is that the membrane wall must simultaneously have two different properties, namely mechanical strength on one hand and on the other hand flexibility in response to small pressure fluctuations between the pressures that prevail on the opposite sides of the membrane wall.
An additional problem occurs when the membrane wall is intended to be in contact with a process fluid. In that case, there are specific requirements with regard to the hygienic construction of the membrane wall and of the control valve as a whole, which means that the side of the control valve that faces the process fluid must not have any spaces that are difficult for a cleaning fluid to access. In additional, there must be essentially no risk of the discharge or escape of the process control fluid through the areas of the membrane wall in which the wall is fastened to the valve housing and to the valve body. This requirement is particularly important in the case of control valves that are used in the foods industry.
U.S. Pat. No. 3,182,678 discloses a control valve of the type described above in which the membrane wall, which comprises two membrane parts, has a support device that is located between the membrane parts. This support device is in the shape of a disc which, starting from the central section of the membrane parts, extends outward in the radial direction for a specified distance. When a support device of this type is used, the load on the membrane parts during the movement of the valve body is so great that the valve as a whole has only a comparatively short useful life. DE 458 931 C2 describes a control valve in which the membrane wall comprises a single membrane part, on the one side of which is located a support device in the form of a disc that is provided with slots that run radially and that covers practically the entire exposed surface of the one side of the membrane part. During the operation of this control valve, the disc-shaped support element is deformed conically by the relative movements between the valve body and the valve housing. Consequently, the outer ends of the membrane parts, which extend beyond the outer periphery of the disc-shaped support element and are clamped inside the valve housing, are subjected to a relatively strong load in the axial direction. When a thin membrane part is used, the useful life of the membrane and of the valve is relatively short.
DE 28 18 633 C2 describes a control valve with a membrane valve which is clamped in a sealed manner in a valve housing in which it separates two chambers from each other, whereby the chambers can be pressurized at different pressures, and with a valve body which is fastened to a central area of the membrane wall and can be moved to act on valve seat in the axial direction by or through the membrane wall, whereby the membrane wall has two separate membrane parts, each of which is located on one side of the membrane wall and faces the corresponding chamber, and a support device is provided between the membrane parts, whereby the support device comprises a plurality of rigid support elements that are separated from one another, and one end of each support element is rotationally connected with the valve body.
EP 1 413 812 A2 also describes a membrane valve with a membrane which is mounted in a sealed manner in a valve housing and separates the control chamber and/or the movable valve stem rod from the product chamber, with a support device for the stabilization of the membrane used.
GB 533 116 describes the configuration of the mounting of a valve spindle through or by a membrane support part.
DE 695 08 865 T2 describes the configuration of a detachable, sealing membrane support and spindle bearing ring.
GB 319 936 and GB 319 961 also show membrane supports that are connected by threaded fasteners to a spindle that can be rotated into a closed position and into an open position and can be driven by it or track its movement. The solution of the object of the present application cannot be inferred from these prior art documents.